From d43d7caf15a01dd9c2ef1d9e975df3ef7c4e9204 Mon Sep 17 00:00:00 2001
From: Clyne Sullivan <clyne@bitgloo.com>
Date: Fri, 27 Sep 2024 06:02:49 -0400
Subject: wip: initial commit

---
 vgaterminal.cpp | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)
 create mode 100644 vgaterminal.cpp

(limited to 'vgaterminal.cpp')

diff --git a/vgaterminal.cpp b/vgaterminal.cpp
new file mode 100644
index 0000000..8158b14
--- /dev/null
+++ b/vgaterminal.cpp
@@ -0,0 +1,54 @@
+#include "portio.hpp"
+#include "vgaterminal.hpp"
+
+#include <algorithm>
+#include <cstddef>
+#include <cstdint>
+#include <utility>
+
+void VGATerminal::write(char c) noexcept
+{
+    switch (c) {
+    case '\n':
+        offset += Width;
+        [[fallthrough]];
+    case '\r':
+        offset -= offset % Width;
+        break;
+    default:
+        checkpos();
+        put(c);
+        updatecursor();
+        break;
+    }
+}
+
+void VGATerminal::put(char c) noexcept
+{
+    std::uint16_t cell = c
+        | (std::to_underlying(foreground) << 8)
+        | (std::to_underlying(background) << 12);
+
+    auto ptr = reinterpret_cast<std::uint16_t *>(Videoram);
+    ptr[offset++] = cell;
+}
+
+void VGATerminal::checkpos() noexcept
+{
+    if (offset >= Width * Height) {
+        auto ptr = reinterpret_cast<std::uint16_t *>(Videoram);
+        const auto end = ptr + Width * Height;
+        std::copy(ptr + Width, end, ptr);
+        std::fill(end - Width, end, 0);
+        offset = Width * Height - Width;
+    }
+}
+
+void VGATerminal::updatecursor() const noexcept
+{
+    outb(0x03d4, 0x0f);
+    outb(0x03d5, static_cast<std::uint8_t>(offset));
+    outb(0x03d4, 0x0e);
+    outb(0x03d5, static_cast<std::uint8_t>(offset >> 8));
+}
+
-- 
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